Bags partially filled with stimuli-responsive highly absorbent superabsorbent polymers for water management and replacement of dams and canals

ABSTRACT

Stimuli-responsive highly absorbent superabsorbent polymers (SAPs) are used to harness water to augment water supply and solve water crisis. Rain water is harnessed in fabric-based sachets or bags partially filled with the polymers. The hydrated polymers are used to store water in warehouses for an extended period of time and the invention may obviate the need to construct controversial huge dams and canals or drill wells. The stored water in superabsorbent polymers is released at the point of use by any stimulus which may be light-induced, electrical, thermal or chemical treatment. SAPs with 2000 g/g of absorbency can yield 99.95% pure water in solid/gel form. An ultra SAP with absorbency of 10,000 g/g of the polymer could hold 10 billion cu.m. of water in one million tonnes of the polymer. This is more than the storage capacity of a typical large dam over a river.

CROSS-REFERENCE TO RELATED APPLICATIONS

Provisional patent application No. 61/403,737 dated Sep. 21, 2010

This is continuation-in-part for my application Ser. No. 13/231,664filed Sep. 13, 2011, now pending.

BACKGROUND OF THE INVENTION

1. Field

This invention relates to use of stimuli-responsive highlysuperabsorbent polymers for harvesting, storage, transportation andretrieval of rain water to obviate the need for dams and canals.

2. Prior Art

Superabsorbent polymers (SAP) are polymers that can absorb and retainextremely large amounts of a liquid relative to its own mass. Lightlycross-linked sodium polyacrylate is the most common type of SAP made inthe world today. Widely used in personal disposable hygiene productssuch as baby diapers, it can absorb about 800 times its weight ofdistilled water. Other SAP compositions include acrylamide copolymers,ethylene maleic anhydride copolymers, crosslinkedcarboxy-methyl-cellulose, polyvinyl alcohol copolymers, crosslinkedpolyethylene oxide and starch grafted copolymer of acrylonitrile.

One of the early patents, U.S. Pat. No. 3,669,103, describescompositions based on lightly cross-linked polymers, such aspolyvinylpyrrolidones, sulfonated polystyrenes, sulfonatedpolyvinyltoluenes, poly-sulfoethyl acrylates, poly-2-hydroxyethylacrylates, polyacrylates, hydrolyzed polyacrylamides and copolymers ofacrylamide with acrylic acid for use in diapers.

U.S. Pat. No. 3,935,099 describes alkali saponifiedgelatinized-starch-polyacrylonitrile graft polymers used as absorbentsfor aqueous suspensions such as sewage sludges.

U.S. Pat. No. 4,286,082 discloses lightly cross-linked sodiumpolyacrylate SAP for use in baby diapers and sanitary napkins.

In U.S. Pat. No. 4,483,950, starch-based superabsorbents extended withmodified starches were promoted as thickening agents.

U.S. Pat. No. 4,913,517 covers uses of SAPs as cable-sealing materials.

U.S. Pat. No. 5,241,009 describes polycarboxyl group containingsuperabsorbents wherein neutralization of said carboxyl groups withpotassium or lithium is described as providing a polymeric compositionspecifically adapted to absorb proteinaceous fluids, such as blood.

U.S. Pat. No. 6,623,645 describes use of SAPS for wastewater containmentand treatment. It does not use stimuli-responsive SAPS. The watercollected is contaminated and cannot be used by humans for normal use.It is not a method to replace dams and canals. The dry contaminatedpolymer is discarded and cannot be reused.

U.S. Pat. No. 6,869,464 describes a device for collecting atmosphericwater at humid locations. It does not teach about collection of water inbags, their storage in warehouses or distribution. It is not a method toreplace dams and canals.

U.S. Pat. No. 6,800,712 discloses SAPS based on grafted starches for usein crop production.

In all above examples, SAPS generally absorb up to 1000 times theirweight of water.

Global demand for SAPS is about 2 million metric tons annually. Morethan 90% is used in disposable hygiene products. Small amounts are usedin agriculture, cable sealing and other niche applications.

Recent research has resulted in some highly absorbent SAPs. Deyu in hisPh.D. thesis “Superabsorbent Polymer Composite Materials and theirIndustrial and High-Tech Applications”, 2003, at Technische Universitat,Bergakademie, Freiberg, Germany describes SAP composites with bentonite(clay) to have water absorbence in excess of over 2000 gram/gram of thecomposite.

Bowling Green State University in the US has reported water absorbancein the range of 2000 to 6000 grams/gram of SAP. The research isdescribed in Thilini K. Mudiyanselage et al, Highly AbsorbingSuperabsorbent Polymer, Journal of Polymer Science: Part A: PolymerChemistry, Vol. 46, 1357-1364 (2008). The same research team at theBowling Green State University has also synthesized photochromic SAPswith water absorbance of 2800 g/g of SAP. When the hydrated photochromicSAP was irradiated with UV light, it expelled the water.

Hitherto, no one has proposed use of SAPs for harvesting and storage ofrain water as replacement of dams and canals.

Advantages

Highly absorbent SAPs have now been developed with absorbency of morethan 6000 times their weight of distilled water. With just 2000 g/g ofabsorbing capacity, we can have at least 99.95% pure water in solid/gelform. Water in solid form can be easily transported and stored anywherewithout leakage or loss. The solid water may be stored in cheap plasticbags in warehouses for an extended period of time. The stored water inSAPs may be released at the point of use by any stimulus which may bechemical, light-induced, electrical, thermal treatment etc.

Accordingly, several advantages of one or more aspects of the inventionare that looming worldwide water crisis can be solved with highlyabsorbent SAPs and water storage in SAPs in warehouses for an extendedperiod of time may obviate the need to construct controversial huge damsand canals or drill wells. In arid lands, dew can be harvested and usedto grow food to reduce hunger. Compared to 13,000 desalination plantsworldwide, producing some 20 billion cu.m. of fresh water annually,equal amount of water can be obtained using only 200 plants eachproducing about 50,000 tonnes of SAP/year with 2000 g/g of absorbency.

Further advantages will become apparent from a consideration of theensuing description.

SUMMARY

In accordance with the invention, one or more aspects of waterharvesting with SAPs are disclosed. Highly absorbent SAPs which arestimuli-responsive are used to harvest rain water to augment watersupply and solve water crisis. The SAPs may be recycled and rehydratednumber of times. They may be an additional source for drinking water.The water is absorbed in fabric-based sachets or bags partially filledwith the polymer. The hydrated SAPs in sachets/bags are used for storageof water in warehouses for an extended period of time and may obviatethe need to construct controversial huge dams and canals or drill wells.The stored water in SAPs is released at the point of use by any stimuluswhich may be chemical, light-induced, electrical, thermal treatment etc.Examples of SAPs include sodium or potassium salts of crosslinkedpolyacrylic acid, salts of crosslinked acrylamide copolymers,starch-acrylonitrile copolymers, composites with clay,stimuli-responsive polymers etc. SAPs with absorbing power of at least1000 times their own weight are preferred. With 2000 g/g of swellingcapacity, we can have at least 99.95% pure water in solid/gel form.

DETAILED DESCRIPTION

SAPs are macromolecules that can absorb and retain extremely largeamounts of a liquid relative to their mass. Lightly cross-linked sodiumpolyacrylate is the most common type of SAP made in the world today.Widely used in personal disposable hygiene products such as babydiapers, it can absorb up to about 800 times its weight of distilledwater. Other SAP compositions include one derived from starch which isone of the oldest SAP developed.

No one has proposed for SAP's use for rain harvesting or watermanagement to replace dams. With just 2000 g/g of absorbing capacity, wecan have at least 99.95% pure water in solid/gel form. Water in solidform can be easily transported and stored anywhere without leakage orloss. The solid water may be stored in warehouses in cheap plastic bagsfor an extended period of time. Looming worldwide water crisis can besolved with highly absorbent SAPs. Water is oil of the future. Suppliesof water are under enormous strain. About 75% of rainfall is lost due torunoff to sea. Rain harvesting with SAPs and storage can augment watersupplies and relieve crisis.

Water in solid/gel form can be transported to any remote part of theworld in low-cost packages or transportation modes such as boxes, gunnybags, carts, open trucks etc. Water stored in SAPs is released at thepoint of use by an appropriate stimulus which may be chemical, UV light,thermal treatment etc. The SAPs may be recycled and rehydrated number oftimes. They are used for storage of water in warehouses and may obviatethe need to construct controversial huge dams and canals or drill wells.An ultra SAP with absorbing capacity of 10,000 gram of water per gram ofthe polymer could hold 10 billion cu.m. of water in 1 (one) milliontonnes of the polymer. This is more than the storage capacity of atypical large dam project over a river.

A typical supply cycle proposed is as follows: 1) Producestimuli-responsive SAPs at strategic locations 2) Distribute SAPgranules to harvesting centers 3) Harvest rain in fabric-based bagspartially filled with SAPs 4) Store hydrated SAPs in warehouses 5)Transport hydrated SAPs to locations of use or water-pumping stations 6)Release water with a stimulus 7) Recycle used polymer. Alternately,individual homes or buildings fitted with commercial rain harvestingsystems can augment their water supplies with these bags containingSAPs.

SAPs can be made available in a variety of forms for harvesting purpose.These include granules, sheet-like structures, fibers and non-wovenwebs. Different types of techniques are described in literature for rainharvesting. These can be augmented with SAPs.

Rain water collected in catchment areas of rain harvesting systems suchas tanks, paved or tiled fields etc are soaked into SAPs and hydratedSAPs stored. One example is use of sachets or bags made of a non-wovenfabric for SAP granules. Sachets/bags of appropriate sizes partiallyfilled with SAP granules are mechanically lowered or passed into raincatchment area. They are almost instantly hydrated with water andsubsequently removed and stored. This whole operation can be mechanized.

Hydrated SAPs are stored in homes or warehouses. They may be transportedto remote arid areas. At the point of use hydrated SAPs are given anappropriate stimulus depending on the polymer type and water released.In one experiment, 0.5 gram of lightly cross-inked sodium polyacrylatewas placed in a 12″×12″ sachet made of a non-woven fabric like one usedfor tea bags. The sachet was soaked in distilled water and it absorbedwater instantly. Fully hydrated SAP weighed about 400 grams. About 2c.c. of a saline solution was sprayed on the sachet. Most of the waterwas instantly released under slight hand pressure.

Dew can be a significant water source but it is lost via evaporation assoon as the sun comes up. In certain coastal arid regions of the world,dew occurs over a period of 8 months in a year. Dew water can beharvested using SAPs. In one method, granules of SAPs or sachetscontaining SAP are spread on a metal and/or plastic sheet, leaving themovernight and collecting hydrated SAP in the morning.

Accordingly, the reader will see that I have provided a solution to thelooming worldwide water crisis by harvesting water in SAPs. With just2000 g/g of absorbing capacity of a highly absorbent SAP, we can have atleast 99.95% pure water in solid/gel form. Water in solid form can beeasily transported and stored anywhere without leakage or loss. Thesolid water may be stored in cheap plastic bags for an extended periodof time in warehouses. The stored water in SAPs may be released at thepoint of use by any stimulus which may be light-induced, electrical,thermal treatment, chemical treatment etc. Water storage in SAPs inwarehouses may obviate the need to construct controversial huge dams andcanals or drill wells. Starch-based highly absorbent SAP or aclay-composite may be made available at low cost for use of thisinvention. Compared to 13,000 desalination plants worldwide, producingsome 20 billion cu.m. of fresh water annually, equal amount of water canbe obtained using only 200 plants each producing about 50,000 tonnes ofSAP/year with 2000 g/g of water absorbency.

While the above description contains some specific examples, theseshould not be construed as limitations on the scope of the invention.Many other ramifications and variations are possible within theteachings of the invention. For example, instead of SAP granules in asachet or bag, SAP in the form of a sheet-like structure, fibers orfabric or the like may be used to harvest water. Instead of chemicalstimulus shown in the above example, sun light or UV light may be usedto release water from a hydrated photochromic SAP. Instead of water fromrain or dew, SAPs may be used to harness water from flood.

Thus the scope of the invention should be determined by the appendedclaims and their legal equivalents, and not by the examples given.

What is claimed is:
 1. A method of harvesting rain water, flood water,or dew with stimuli-responsive superabsorbent polymers (SAPs),comprising: (a) partially filling fabric-based bags or sachets withSAPs; (b) distributing the SAP filled fabric-based bags or sachets to aharvesting center; (c) contacting the SAP filled fabric-based bags orsachets with floodwater, rain or dew at the harvesting center; (d)harvesting rain or dew with the SAP filled fabric-based bags or sachetsby absorbing water from the rain or dew to form hydrated SAP filledfabric-based bags or sachets; (e) storing hydrated SAP filledfabric-based bags or sachets in bags in warehouses for a period of time;(f) transporting hydrated SAP filled fabric-based bags or sachets inbags from warehouses to a point of use; and (g) releasing water fromhydrated SAP filled fabric-based bags or sachets with a stimulus.
 2. Themethod of claim 1, wherein superabsorbent polymer is in the form ofgranules or powder placed in sealed fabric-based sachets or bags.
 3. Themethod of claim 1, wherein the hydrated SAP filled fabric-based bags orsachets are be placed in protective plastic bags during transportationand storage to prevent water evaporation.
 4. The method of claim 1,wherein water in hydrated superabsorbent polymers is released at pointof use by a stimulus which is selected from the group consisting ofchemical, thermal, electrical, and exposure to sun or UV light.
 5. Amethod of claim 1, where the superabsorbent polymer is selected from thegroup consisting of sodium or potassium salts of crosslinked polyacrylicacid, salts of crosslinked acrylamide copolymers, starch-acrylonitrilecopolymers, composites with clay, stimuli-responsive superabsorbentpolymers.
 6. The method of claim 1, wherein the superabsorbent polymershave a water retention of at least 1000 grams of water per gram ofsuperabsorbent polymer.
 7. The method of claim 1, wherein after thewater is released from hydrated SAP, the water is consumed by humans.